Kinetics of substitution

Empirical approach to ligand effects on the kinetics of substitution and redox reactions. V. Gut-mann and R. Schmid, Coord. Chem. Rev., 1974,12, 263-293 (90). 

It has long been known that substitution at the anion of Zeise s salt, [Pt(CH=CH2)Cl3], is, thanks to the high trans effect of the coordinated ethene, very fast. Recent developments in low-temperature stopped-flow apparatus have now permitted the study of the kinetics of substitution at Zeise s and other [Pt(alkene)Cl3] anions in methanol solution. These substitutions obey the customary two-term rate law (i.e. with kohs = ki+ /s3[nucleophile]), with large negative AS values for the k2 term as expected for Sn2 processes (196). 

The ability of vanadium(II) chloride to facilitate sulfoxide deoxygenation has been discussed (Section IV,C), and it appears that vana-dium(III) sulfoxide complexes may be prepared by air oxidation of van-adium(II) salts in the presence of the sulfoxide. In this manner, [V(Me2S0)6][C104]3 was prepared from vanadium(II) perchlorate (119) and the kinetics of substitution with thiocyanate ion detailed. Care is necessary in handling the pure compound, as it is reported to be sensitive to detonation. A large number of oxovanadium(IV) species have... 

The second-order redox reaction, giving rise to the rate constant k2, is accompanied also by loss of the iron(II) complex by hydrolysis, which leads to the /tj term. The latter can be more accurately measured in the absence of Tl(III). The kinetics of substitution of many square-planar complexes conform to behavior (c), see Sec. 4.6. It is important to note that an intercept might be accurately defined and conclusive only if low concentrations of B are used. In the base catalyzed conversion... 

The substitution process permeates the whole realm of coordination chemistry. It is frequently the first step in a redox reaction and in the dimerization or polymerization of a metal ion, the details of which in many cases are still rather scanty (e.g. for Cr(III) ). An understanding of the kinetics of substitution can be important for defining the best conditions for a preparative or analytical procedure. Substitution pervades the behavior of metal or metal-activated enzymes. The production of apoprotein (demetalloprotein and the regeneration of the protein, as well as the interaction of substrates and inhibitors with metalloproteins are important examples. ... 

The Ad -E mechanism proposed to account for the kinetics of substitution of 9-(a-bromo-a -arylmethylene)fluorenes by thiolate ions in aqueous acetonitrile also features elimination of the leaving group in a fast step following rate-determining carbanion formation (by nucleophilic addition). ... 

Advances in the chemistry of [M(CN)5L]" complexes, for M = Fe, Ru, and Os, have been reviewed.There has been rather little activity in the preparation of novel complexes, but considerable activity in studying the properties, especially solvatochromism and various aspects of kinetics of substitution, of known complexes. However there has been an attempted preparation of [Fe(CN)5(Ci2H25NH2)], in the hope of generating micelles or lyotropic liquid crystals. This preparation appeared to yield [Fe(CN)4(H20)(Ci2H25NH2)], whose alkali metal salts gave a hexagonal mesophase in water, but were also readily hydrolyzed to [Fe(CN)4(H20)2] . Heterobinuclear complexes of the form [(NC)5FeL ML 5] " " have been much studied, especially in relation to intramolecular electron transfer (see Section 5.4.2.2.5). 

One of the earliest studies of the kinetics of substitution reactions of square planar complexes is that of the Cl exchange of [AuClJ- (22). A two-term rate law was found for the exchange rate and it was suggested that this may prove to be general behavior for square complexes. 

Brown, S. C., Grady, C. P. L., Jr Tabak, H. H. (1990). Biodegradation kinetics of substituted phenolics demonstration of a protocol based on electrolytic respirometry. Water Research, 24, 853-61. 

In this Chapter are described the possible mechanisms of electrophilic substitution at saturated carbon, as a preliminary to the discussion of the kinetics of substitution. Additionally, there is a description of the nomenclature that has been used to date. There has been no general agreement on the nomenclature of the mechanisms of electrophilic substitution at saturated carbon, and the notation used in subsequent chapters in the present work can thus usefully be enumerated here. We deal first of all with the fundamental mechanisms, that is with mechanisms that do not involve rearrangement or nucleophilic (anionic) catalysis. 

The attachment to the metal center of the second or third donor atom of the ligand is usually very rapid, so in most cases departure of the first water molecule is rate determining. The rate-determining step is the closure of a chelate ring in complex formation reactions where a steric property of the ligand governs the kinetics of substitution by the second donor atom.241,242 In cases in which Equation 7.21 is applicable, the volume of activation is given by... 

The kinetics of substitution of the chelate group by tu, glutathione, and guanosine-5 -monophosphate and, in the case of the first two compounds by L-Met, on the compounds [Pt(dach)(CBDCA)], [Pt(dach)(gly)j+, and [Pt(dach)(L-Met)]+ have been investigated. Direct substitution of the chelate was observed and the nature of the donor atoms of the chelate (O-O, N-O, or S-N) plays an important role. Large... 

In the case of technetum, this is the most practically used element among non-/ radioactive ones for medical and technical purposes [283], so the permanent interest in its coordination chemistry (in particular, the structural aspect of its compounds [547] and kinetics of substitution reactions [548]) is not surprising [549]. The theoretical interest in Tc is provoked, in particular, by the fact that this is a rhenium analogue. This element (Re) forms multiple metal-metal bond complexes and has been studied intensively in order to achieve a better understanding of the physical and chemical properties of multiple bonds between metal atoms [533],... 

The purpose of this chapter is to explore the properties and reactions of various Pt-nucleobase complexes. After a short description of various binding modes, attention will be paid on the effects of coordinated platinum. Topics include, e.g., isomerization, thermodynamic stability, and solvolyt-ic reactions of Pt-nucleobase complexes. Finally, factors affecting the mechanism and kinetics of substitution reactions by various nucleophiles will be discussed. 

Bunton and de Buzzaccarini have studied the kinetics of substitution reactions in microemulsions and compared the result with the reaction kinetics in... 

Fig. 2.14 Fred Basolo (1920-2007) was the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern University in Evanston in the US. He worked for his Ph.D. with one of the founders of coordination chemistry in the US, John C. Bailar, and received a doctorate from the University of Illinois in 1943. After working on then-classified projects for the war effort, he joined the chemistry department at Northwestern in 1946, where he was a force to be reckoned with for more than 60 years. Together with Ralph Pearson, he was one of the pioneers in the field of inorganic reaction mechanisms and one of the first studying the kinetics of substitution reactions of metal carbonyls. He coauthored two text books Mechanisms of Inorganic Reactions (with R. G. Pearson) and Coordination Chemistry (with R. C. Johnson). Fred was elected to the National Academy of Science in 1979, was the President of the American Chemical Society in 1983, and received the Priestley Medal, the highest award of the ACS, in 2001 (photo by courtesy from Professor Jim Ibers, Northwestern University)...

In the 1930s, Sir Christopher Ingold and co-workers at the University of London studied the kinetics of substitution reactions such as the following ... 

The kinetics of substitution of bipy or phen into Co (467, 574), Ni (144), and Pt (697) complexes have been reported. Several studies of the hydrolysis of complexes of form [Co(III)(bipy)2XY] may be found. For both cis and trans isomers where X = Y = CY, hydrolysis is instantaneous (581), whereas for the cis isomer with X = acetate and Y = acetate or OH , reaction is very slow as a conjugate base mechanism cannot operate and the first-order reaction is therefore independent of [OH ] (124). One NO2 group in acid dependent and under acidic conditions is thought to proceed via protonation of one nitro group (289, 472). The interconversion of the cis and trans isomers, where X = N02 and Y = H2O, has an overall rate constant equal to + A [H+], implying reactions for both OH and... 

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